Co-pyrolysis Of Polymeric Waste And Biomass For Improved Pyrolysis Products

The increasing amount of polymeric waste,waste tire,and plastics,has raised several environmental concerns.As these wastes are the known cause of extensive environmental problems,which can be detrimental to the biota and for the lives of human beings.It has been reported that about 1.6 billion pieces of tires are supplied annually,which is estimated to reach up to 2.9 billion by the end of 2020.And the manufactured tires eventually end up as a waste/scrap material.In addition,the global production of plastics has also increased in the past few decades,about 183 times,from1.7 million tons in the 1950s to 311 million tons in 2015.And it is expected to increase more by the addition of 33 billion tons till 2050.Therefore,it is important to tackle this issue through effective treatment method.Besides,polymeric wastes are also the known hydrocarbon waste fractions having hefty potential in terms of valued products recovery though thermochemical conversion method.And the pyrolytic conversion of polymeric waste into the liquid product is a viable option.However,the pyrolysis oil from certain waste fractions contains high amount of pollutants including PAHs,nitrogen and sulfur-containing compounds.And the certain properties make it unsuitable as blending constituent for further upgradation.In this regard,the utilization of biomass with polymeric waste during co-pyrolysis can significantly influence the undesirable compounds as the addition of lignocellulose biomass is associated with further pollutants reduction.Moreover,it is also important to consider the occurrence of synergistic effects while employing different co-pyrolysis conditions.And to explore the possible interactive effect,hydrogen/carbon effective(H/C_eff)ratio could be employed during the process concerning the product quantity and quality.This research was aimed to study the influence of varying hydrogen/carbon effective ratio（H/Ceff）during co-pyrolysis of different polymeric waste and biomass.In this regard,waste tire（WT）and polystyrene（PS）were separately mixed with sawdust（SD）at varying H/Ceff ratios to investigate the possible synergistic effects during co-pyrolysis for significant quantity and quality improvement concerning the product distribution.The thermal degradation characteristics of different blends at varying H/Ceff ratios were scrutinized by using a thermo-gravimetric analyzer（TGA）coupled with Fourier transform infrared（FTIR）.And the pyrolysis experiments of single and blended fractions were conducted in a fixed-bed reactor at different temperatures（500℃,550 ℃,and 600 ℃）.The nitrogen flow was maintained at 100ml/min,and the reaction time was 30 min.1-The obtained results disclosed that the addition of SD in WT accelerated the degradation rate while resulting in more weight loss at a relatively low temperature.The maximal liquid yield of the WT/SD blend was attained at 0.42 H/Ceff with 46.67%at 500 ℃,which was even higher than the liquid pyrolysis yield of WT（45.05%）.It was perceived that the lignocellulose biomass could act as an accelerator for waste tire decomposition and waste tire act as hydrogen-donor for further upgradation of products.Besides,the temperature gradient also had a considerable effect on mixing ratios.As the total percentage of valued aromatic hydrocarbons in WT/SD blends exhibited the increasing trend from lower to higher H/C_eff（0.21–0.62）,respectively.And the relative values were also increased with the increasing temperature.The total percentage of hydrocarbons in WT/SD blends were maximized at 0.62 H/Ceff,with83.2%at 550 ℃.Whereas the optimal ratio for WT/SD blends was considered as 0.42H/Ceff at 500 ℃ due to reduced pollutants and maximized liquid yield.2-The optimal H/Ceff ratio from PS/SD co-pyrolysis was obtained at 0.64 H/Ceff and at 500 ℃ with increased hydrocarbons and reduced PAH.The pyrolysis oil obtained from PS/SD blends also improved the production of hydrocarbons.With the increasing H/Ceff,the total percentage of hydrocarbons in PS/SD reached up to 89.02%at 550 ℃ with 0.64 H/Ceff.And the certain substantial increment was also greater than the total percentage of hydrocarbons produced in polystyrene with 88.92%at 550 ℃.3-The relative total percentage of undesired compounds（UC）in WT/SD blends was also less than the total values of UC in waste tire oil.Similar results were also obtained with polystyrene.As the addition of sawdust with increasing H/Ceff significantly reduced the nitrogen and sulfur compounds.The total percentage of nitrogen-containing compounds in WT/SD blends at 0.21 H/Ceff was 0.3%as compared to total values in WT oil with 2.2%.Whereas,at higher H/Ceff values,these compounds were not even generated.The nitrogen-containing compounds also disclosed the similar trends at 500 ℃ and 600 ℃.In addition,the sulfur compounds were also decreased at varying mixtures as compared to WT oil having 6.04%.The results presented relative lower concentrations at even higher H/Ceff ratios,and a similar trend was observed at elevated temperatures.Hence,the increasing H/Ceff ratio presented the concerning improvements in results.Moreover,the addition of sawdust also assured the improvement in pyrolysis oil quantity and quality in terms of reduction in undesired compounds,including polyaromatics,N-containing and S-containing compounds.And the certain quality improvement can contribute to the enhancement of combustion efficacy of pyrolysis oil.